Section 13 — Plant Genetics and Breeding 



logic race 1 1 1 (the most widely avirulent of the 

 described physiologic races) was used because a 

 culture avirulent on a wide spectrum of varieties 

 would be expected to differentiate more re- 

 sistance genes than a virulent one. The Fi, F2, 

 F3, backcross-Fi, and backcross-F2 generations 

 from crosses of resistant tetraploid varieties 

 Acme, Arnautka, Kubanka, Mindum, Vernal, 

 and Khapli with moderately susceptible P.I. 

 192334, and from crosses of resistant hexaploid 

 varieties Marquis and Kota with susceptible 

 Little Club were tested with a single spore 

 culture of physiologic race 111. Two resistance 

 genes in Kubanka and three in each of the other 

 resistant varieties were indicated. All of the 

 resistance genes were dominant or partially 

 dominant. Genes for high levels of resistance 

 commonly appeared epistatic to genes for low 

 levels of resistance. In some cases, notably in 

 Vernal, the resistance genes were cumulative in 

 effect. 



1. Cooperative investigations at Fargo, North 

 Dakota, of the Crops Research Division, 

 ARS, USDA 5 and the North Dakota Agri- 

 cultural Experiment Station. 



13.49. A Monosomic Analysis of Leaf Rust Resistance 

 in Five Varieties of Triticum aestivum L. 



R. C. McGinnis and W. J. R. Boyd (Winni- 

 peg, Canada). 



Five leaf rust resistant varieties of common 

 wheat (Africa 43, Frontana, Klein Aniversario, 

 Klein Titan, and Sinvalocho) were crossed to all 

 21 different monosomies of the susceptible 

 varieties Red Bobs and Rescue, as well as in 

 diallel in order to investigate the inheritance of 

 rust reaction and associate genes for resistance 

 with specific chromosomes. Chromosome counts 

 made from root-tip squashes of germinated Fi 

 seed prior to planting were used to identify 

 monosomic and disomic plants. The Fi's were 

 inoculated with race 9 of Puccinia recondita 

 Rob. ex Desm. at both seedling and adult stages 

 and rust reactions recorded. In the seedling 

 stage, resistance proved to be recessive in all 

 cases; segregation for resistance occurred in 

 only the critical chromosome lines. It was 

 possible, therefore, to associate genes for re- 

 sistance with specific chromosomes as follows: 

 Africa 43 — chromosomes IB and 5D; Frontana 

 — 2A and 5A; Klein Aniversario and Sinvalocho 

 5A, 4B and 5D; and Klein Titan— 4B, 4D and 



5D. Resistance was found to be dominant at the 

 adult plant stage. 



F2 populations from monosomic Fi plants 

 together with disomic controls were grown and 

 also inoculated at seedling and adult stages. The 

 data showed that the inheritance of adult plant 

 reaction is complex and expression of reaction 

 is influenced greatly by environment. No satis- 

 factory genetic hypothesis could be proposed for 

 the different varieties on the basis of the available 

 data. Chromosome 5A of all varieties appeared 

 to carry a gene for adult plant resistance and is 

 particularly important in Frontana while chro- 

 mosome 6B appeared to be important to all 

 varieties except Frontana. 



13.50. Genetic Studies on Geographical Distribution 

 of Barley Varieties with Special Reference to 

 Uzu or Semi-brachytic Form Native to Japan. 



Ryuhei Takahashi (Kurashiki, Japan). 



The present writer has already shown that 

 about 80 per cent of barley acreage in Japan is 

 now occupied by a group of varieties which 

 possess in common a recessive mutant gene 

 called uzu (uz). They are characterized by short, 

 thick culms and compact heads with short awn, 

 which are especially preferred by the Japanese 

 farmers. A further study was made to gather 

 more evidence for the prevalence of this type in 

 Japan. For this, effects of the genes, Uz and 

 uz, on yield and its components were compared 

 using 24 normal and uzu isogenic paired lines. 

 The results indicated that uz was slightly less 

 favorable than Uz in an average genetic back- 

 ground. However, productivity of uzu relative 

 to normal line was found to vary considerably 

 with genetic background. Thus, possibility of 

 breeding higher yielding uzu variety by selecting 

 good genetic background was suggested. Re- 

 sponses of several selected isogenics to three 

 different levels of fertility disclosed that uzu 

 barley was adaptive to heavy manured con- 

 ditions, but was inferior to the normal one at the 

 lower levels of fertility. It may be possibly 

 concluded that progress in barley breeding and a 

 marked trend of heavy manuring have fostered 

 the spread of uzu barley, replacing the formerly 

 existing normal type varieties. 



13.51. Breeding Lodging Resistant Winter Barleys 

 from "Uzu" Parentage. John M. Poehlman 

 (Columbia, U.S.A.). 



Lodging resistant winter barleys with short, 



226 



